### Author Topic: question on transistor simulation tutorial  (Read 199 times)

0 Members and 1 Guest are viewing this topic.

#### rose

• Regular ATK user
• Posts: 47
• Country:
• Reputation: 0
##### question on transistor simulation tutorial
« on: October 11, 2020, 17:16 »
hi everyone,
I try to simulate graphene nanoribbon transistor ( z shape ) as mentioned in the tutorial. I do some calculations and I got a problem in the interpretation of what is happening in this tutorial. I would wonder if someone can help me. ( in the device3.py in this tutorial there is a hydrogen atom which should be removed.)

The result shows a very low transmission in -1 to 1 eV range (Vg=0) using GGA-SZP which is in good agreement with Armchair GNR bandgap IF we consider it very long along z-direction, but in this tutorial, we are studying an armchair in z shape which is very short and if we just split this device3.py and add 20 angstrom to the center and getting bandstructure we will see that the bandgap is reduced to 0.2eV which means that due to quantum confinement along z-direction the new (z shape armchair ) has small bandgap which is not in agreed with the transmission results.
I can not understand the channel is considered as a  long armchair ? or is it a small one? or due to very little subbands forming a 0.2 eV gap in this quasi-quantum dot armchair shape structure! we can not get the transmission around it?

thanks
Rose

#### RaulAlonso

• New ATK user
• Posts: 1
• Country:
• Reputation: 0
##### Re: question on transistor simulation tutorial
« Reply #1 on: December 30, 2020, 10:46 »
Same question here

#### Petr Khomyakov

• QuantumWise Staff
• Supreme ATK Wizard
• Posts: 1271
• Country:
• Reputation: 24
##### Re: question on transistor simulation tutorial
« Reply #2 on: January 8, 2021, 11:25 »
The result shows a very low transmission in -1 to 1 eV range (Vg=0) using GGA-SZP which is in good agreement with Armchair GNR bandgap IF we consider it very long along z-direction, but in this tutorial, we are studying an armchair in z shape which is very short and if we just split this device3.py and add 20 angstrom to the center and getting bandstructure we will see that the bandgap is reduced to 0.2eV which means that due to quantum confinement along z-direction the new (z shape armchair ) has small bandgap which is not in agreed with the transmission results.
I can not understand the channel is considered as a  long armchair ? or is it a small one? or due to very little subbands forming a 0.2 eV gap in this quasi-quantum dot armchair shape structure! we can not get the transmission around it?

Could you provide more information on this calculation, python script, log file and possibly hdf5 output or transmission plot at least? What is the QunatumATK version you are using?